Donna Shirley: David, making a planet habitable is something that people have said is maybe a good thing to do, maybe not a good thing to do. And the question is, since your research is on climate evolution and habitability, can we do it?

David Grinspoon: Can we do it? I think that, in the long run, we probably could if we wanted to, from a technical point of view. But my concern is not over the technical difficulty, but the societal problems. I think that human technical ability increases fast; it increases exponentially. Human wisdom increases much more slowly.

But, to my mind, I think that if a hundred years from now, we decided that we wanted to terraform Mars, we would know how to do it. We already have some ideas, and we’re getting smarter all the time about how planetary climate works from a technical point of view.

But whether we have the other abilities that we need, in terms of the collective decision-making that it takes to purposefully transform a planet, right now we’re having trouble purposely not transforming our own planet. We’re having trouble not veneraforming the Earth, in a sense. And I think if we get to the point where we demonstrate that we have the wisdom to take care of Earth’s climate, and not haphazardly, but in a collective way, where we decide that we’re going to make these decisions and we’re able to control Earth’s climate, then maybe we will have the wisdom to terraform Mars.

We should be thinking about terraforming Mars. I don’t think we should terraform Mars now, but as we think about it, we work the problem of how do we purposefully take care of a planetary climate. So I think that this exercise of considering terraforming Mars is very good for us, and is maybe a first step towards attaining the kind of wisdom that we need to someday be smart enough – not just technically, but also ethically and in terms of collective decision-making – to terraform Mars.

Donna Shirley: Stan, you’ve written about all those things. One of the things that you’ve written about is the role of Antarctica in preparing us to go to Mars. What would you say about the question of should we do it, and what should we do?

Kim Stanley Robinson: I think that Antarctica will serve as a good analog for Mars. (Mars) will be a distant place that’s cold. There will be scientific stations there. And it’ll be interesting to the rest of humanity, but somewhat remote. Scientists will be rotating crews coming back after their stay. And what we learn there will teach us more about taking care of the Earth. So, if you want to think about what Mars can be compared to in the rest of human history, because in many ways it’s entirely a new thing, I think Antarctica is a much better model than the Wild West or any other model that’s been proposed.

But this question of should we terraform or not, I find it really interesting because the scientists are still split on the question of whether we have any good expectation of finding indigenous life there. So it becomes a kind of decision-tree that we have to answer – like forks in paths, we have to come to a fork, find a way to make a decision, and then move on to the next decision.

The first question we need to answer is, is there life there right now alive, or not? When we answer that, and if the answer’s in the negative, we can then proceed with essentially a dead rock that’s very big and really interesting, and bringing life seems the obvious thing to do. A project which the industrial capacities of humanity may grow in ways that are as surprising to us as (our technology would be surprising to) the people in the 17th century.

"We are co-habitating with organisms that live very much in partitioned ecosystems, where organisms from one cannot survive in the other." -Lisa Pratt
Image credit: Woods Hole Ocean. Institute

If we do find life on Mars, it will be very interesting to try to discover whether it is indigenous, which is to say a second start, and truly alien to us, a second genesis. In that case, I think we’ll have to go and try to kill all the bacteria that are already there, inside the boxes that we’ve left, and try to clean up and really study it from a distance. That will be a really remarkable discovery, perhaps the major discovery in human history.

But if we find that the life there has the same DNA, the same patterns, and is clearly bacteria that got bounced up there from Earth, or vice versa, and that we’re all martian bacteria that got bounced down here and then evolved – if they’re cousins, in a sense, then I think you could go on for a few centuries and begin to feel that we could move to Mars and live on Mars. The local cousins would have their niches, and we would have our niches, and then let the two begin to interpenetrate again.

At each point we need to make these decisions without being able to say right now, "Oh, we should terraform Mars," or, "Oh, we shouldn’t terraform Mars." We can’t answer that yet. But I agree that it is a completely useful thought experiment. Because it’s really the terraforming of Earth that we are now doing, in ignorance and by accident. And so we need to know more about it.

Donna Shirley: Lisa, you found cave creatures way down below the Earth. Can they co-exist with the creatures on the surface? Seems like a Mars analog to me.

Lisa Pratt: I think certainly on Earth, as we begin to look at greater and greater depths and into increasingly extreme environments, we realize that we are co-habitating with organisms that live very much in partitioned ecosystems, where organisms from one cannot survive in the other. So, in that sense, one can perhaps imagine a situation where there would be indigenous martian organisms that continue to reside in the deep subsurface, relatively protected and isolated.

"The vast majority of microbial organisms remain unculturable, even on planet Earth." -Lisa PrattImage Credit: NSF/John Priscu, Montana State University

But I think the problem for us as a scientific community, and the problem for the public as a whole, is that until we know enough about the subsurface of Mars to make an informed decision, it’s really difficult to move forward. Right now, we barely know enough about the subsurface of Earth to make informed decisions. We’re discovering, practically on a daily basis, organisms in places that we, as recently as 10 years ago, were absolutely certain were barren of life.

As we have begun to get samples back that are clean enough of surface contamination to think that we’re actually looking at deep subsurface materials, what we realize is we know the organisms are there because we can identify their genes, but we can’t culture most of these organisms. So we don’t in fact know what their requirements for life are. In some cases, we know what their energy source is. In some cases we know what their carbon source is. But the vast majority of microbial organisms remain unculturable, even on planet Earth.

Donna Shirley: John, if subsurface microbes are unculturable, how do you know when there is life there or not? How do we know when we can safely assume Mars is dead and start terraforming?

John Rummel: Well, the good news is that life, when it’s there, tends to leave little dead life around. So you can pick out the dead bug bodies. They play hell with organic chemistry, and that’s a good thing. But they also change the environment around them. Basically, you’re moving material and energy around, back and forth, to attain some particular end, usually the result is more microbes of one kind or another. And even if we can’t grow them, it doesn’t mean that they can’t grow.

Our attempts to culture microbes are a little bit like trying to grow large mountain lions by feeding them wheat. It doesn’t work very well, and it really ticks them off. I understand mountain bikers is a better diet, but that’s a California joke.

The Planetary Fourier Spectrometer (PFS).Image Credit: ESA

I really think that eventually we will find out whether or not there is something there by their action on their own environment. But it will be critical to know these things before we attempt to modify the martian environment at all. And I think if we watch Mars for just a little bit while longer, even if there’s nothing alive there, there are things going on. And those things may or may not lead you to a deduction that life is there.

We have people now reporting methane in the atmosphere. This is a detection from the planetary Fourier spectrometer. ESA, the European Space Agency, has put out an announcement that it’s been detected at 10 to 20 parts per billion. Well, methane in the atmosphere on Mars can mean one of three things: either vulcanism, possibly microbial life, or maybe cows. We haven’t seen the cows yet. I doubt that we’ll find them. But one of the other two would be a very interesting thing to find out.

Whether or not we can find more methane on one part of Mars than another is going to take either more measurements from abroad or an instrument in-situ, perhaps in orbit around Mars, that can really make high-definition measurements. So these are things for people to propose for future Scout opportunities or future Discovery opportunities to really nail it down. Then we’ll have to go to those places and find out what’s going on there. When we do, we don’t want to take our own bacteria there so that they do those things themselves. We want to find out about Mars life before we take Earth life to a place where it can be modifying the environment in a way that we can’t control. We’re not trying to control Mars and martian life right now. If we ever want to, we want to make sure we don’t screw it up first.